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CastCheck methodology v0.2 · data through 2026-08-30

Seattle-Tacoma · GraphCast (IFS init) · lead day 5

KSEA · graphcast_ifs · lead 5

Target day = initialization date + 5 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, GRAP_v100, starting 2026-01-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d25 1 QC5.61 [4.16, 7.38]3.34-5.25 [-7.30, -3.24]6.70 [5.01, 8.50]4% [0%, 15%]20%24%+0.05+0.412026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC5.61 [3.97, 7.48]3.34-5.25 [-7.44, -3.00]6.70 [4.83, 8.58]4% [0%, 18%]20%24%+0.05+0.412026-08-06 → 2026-08-30
tmax00Zbilinear365d31 1 QC4.96 [3.13, 6.95]3.29-4.49 [-6.82, -2.27]6.11 [3.92, 8.07]10% [0%, 27%]23%32%+0.16+0.432026-01-06 → 2026-08-30
tmax00Zbilinearall31 1 QC4.96 [3.09, 6.71]3.29-4.49 [-6.63, -2.15]6.11 [3.87, 7.89]10% [0%, 28%]23%32%+0.16+0.432026-01-06 → 2026-08-30
tmax00Znearest30d25 1 QC5.77 [4.27, 7.56]3.40-5.42 [-7.48, -3.36]6.85 [5.15, 8.68]0% [0%, 0%]20%28%+0.03+0.402026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC5.77 [4.11, 7.64]3.40-5.42 [-7.61, -3.13]6.85 [4.99, 8.73]0% [0%, 0%]20%28%+0.03+0.402026-08-06 → 2026-08-30
tmax00Znearest365d31 1 QC5.10 [3.24, 7.08]3.33-4.66 [-7.01, -2.41]6.26 [4.01, 8.20]3% [0%, 12%]23%35%+0.13+0.422026-01-06 → 2026-08-30
tmax00Znearestall31 1 QC5.10 [3.19, 6.86]3.33-4.66 [-6.82, -2.29]6.26 [3.94, 8.07]3% [0%, 12%]23%35%+0.13+0.422026-01-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC5.66 [4.25, 7.17]2.70-5.38 [-7.12, -3.71]6.38 [4.85, 7.79]4% [0%, 15%]16%16%+0.04+0.522026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC5.66 [4.04, 7.29]2.70-5.38 [-7.21, -3.50]6.38 [4.54, 7.90]4% [0%, 18%]16%16%+0.04+0.522026-08-06 → 2026-08-30
tmax12Zbilinear365d30 1 QC5.08 [3.17, 6.82]2.91-4.74 [-6.60, -2.61]5.93 [3.82, 7.44]7% [0%, 20%]27%27%+0.13+0.482026-01-06 → 2026-08-30
tmax12Zbilinearall30 1 QC5.08 [3.01, 6.73]2.91-4.74 [-6.58, -2.52]5.93 [3.69, 7.41]7% [0%, 21%]27%27%+0.13+0.482026-01-06 → 2026-08-30
tmax12Znearest30d25 1 QC5.77 [4.37, 7.26]2.66-5.51 [-7.24, -3.83]6.48 [4.94, 7.89]0% [0%, 0%]16%16%+0.02+0.532026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC5.77 [4.17, 7.39]2.66-5.51 [-7.33, -3.63]6.48 [4.67, 7.97]0% [0%, 0%]16%16%+0.02+0.532026-08-06 → 2026-08-30
tmax12Znearest365d30 1 QC5.19 [3.24, 6.90]2.88-4.89 [-6.71, -2.79]6.04 [3.96, 7.53]3% [0%, 13%]23%27%+0.11+0.492026-01-06 → 2026-08-30
tmax12Znearestall30 1 QC5.19 [3.11, 6.82]2.88-4.89 [-6.71, -2.73]6.04 [3.80, 7.51]3% [0%, 14%]23%27%+0.11+0.492026-01-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC1.90 [1.19, 2.53]1.19+1.89 [1.18, 2.52]2.34 [1.57, 2.84]36% [17%, 55%]60%68%+0.18+0.482026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC1.90 [1.16, 2.60]1.19+1.89 [1.16, 2.58]2.34 [1.51, 2.89]36% [14%, 57%]60%68%+0.18+0.482026-08-06 → 2026-08-30
tmin00Zbilinear365d31 1 QC1.90 [1.31, 2.52]1.22+1.87 [1.25, 2.49]2.34 [1.67, 2.83]35% [18%, 53%]58%71%+0.28+0.542026-01-06 → 2026-08-30
tmin00Zbilinearall31 1 QC1.90 [1.28, 2.49]1.22+1.87 [1.26, 2.45]2.34 [1.64, 2.83]35% [18%, 53%]58%71%+0.28+0.542026-01-06 → 2026-08-30
tmin00Znearest30d25 1 QC1.68 [1.03, 2.30]1.23+1.55 [0.80, 2.22]2.12 [1.37, 2.62]44% [20%, 70%]64%68%+0.28+0.472026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC1.68 [0.96, 2.36]1.23+1.55 [0.72, 2.30]2.12 [1.29, 2.65]44% [20%, 72%]64%68%+0.28+0.472026-08-06 → 2026-08-30
tmin00Znearest365d31 1 QC1.73 [1.16, 2.30]1.27+1.55 [0.90, 2.20]2.15 [1.51, 2.61]42% [20%, 65%]65%71%+0.35+0.522026-01-06 → 2026-08-30
tmin00Znearestall31 1 QC1.73 [1.12, 2.27]1.27+1.55 [0.89, 2.18]2.15 [1.48, 2.60]42% [21%, 65%]65%71%+0.35+0.522026-01-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC2.02 [1.27, 2.72]1.18+2.00 [1.22, 2.72]2.43 [1.54, 3.01]32% [18%, 48%]60%68%+0.13+0.492026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC2.02 [1.16, 2.80]1.18+2.00 [1.12, 2.79]2.43 [1.36, 3.07]32% [18%, 50%]60%68%+0.13+0.492026-08-06 → 2026-08-30
tmin12Zbilinear365d30 1 QC2.13 [1.37, 2.83]1.36+2.02 [1.30, 2.75]2.61 [1.72, 3.25]30% [17%, 43%]57%67%+0.19+0.482026-01-06 → 2026-08-30
tmin12Zbilinearall30 1 QC2.13 [1.30, 2.85]1.36+2.02 [1.21, 2.74]2.61 [1.59, 3.26]30% [17%, 44%]57%67%+0.19+0.482026-01-06 → 2026-08-30
tmin12Znearest30d25 1 QC1.86 [1.11, 2.54]1.22+1.71 [0.87, 2.49]2.25 [1.36, 2.82]36% [20%, 53%]60%76%+0.20+0.472026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC1.86 [0.95, 2.60]1.22+1.71 [0.76, 2.57]2.25 [1.16, 2.88]36% [18%, 55%]60%76%+0.20+0.472026-08-06 → 2026-08-30
tmin12Znearest365d30 1 QC2.00 [1.24, 2.67]1.41+1.73 [0.92, 2.51]2.47 [1.53, 3.17]33% [18%, 50%]60%73%+0.24+0.462026-01-06 → 2026-08-30
tmin12Znearestall30 1 QC2.00 [1.17, 2.73]1.41+1.73 [0.83, 2.51]2.47 [1.41, 3.17]33% [17%, 50%]60%73%+0.24+0.462026-01-06 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for GraphCast (IFS init) at KSEA, lead day 5, 00Z bilinear tmax+20+100-10-202026-08-06: -9.91 °F2026-08-07: -1.71 °F2026-08-08: -4.73 °F2026-08-09: +1.44 °F2026-08-10: +3.07 °F2026-08-11: -3.13 °F2026-08-12: -3.68 °F2026-08-13: -10.75 °F2026-08-14: -1.07 °F2026-08-15: -2.13 °F2026-08-16: -1.06 °F2026-08-17: -10.38 °F2026-08-18: -9.39 °F2026-08-19: -14.69 °F2026-08-20: -11.35 °F2026-08-21: -4.29 °F2026-08-22: -7.48 °F2026-08-23: -6.83 °F2026-08-24: -5.56 °F2026-08-25: -3.99 °F2026-08-26: -6.32 °F2026-08-27: -5.4 °F2026-08-28: -4.1 °F2026-08-29: -6.68 °F2026-08-30: -0.99 °F2026-08-062026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (25 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.99
2026-08-29-6.68
2026-08-28-4.10
2026-08-27-5.40
2026-08-26-6.32
2026-08-25-3.99
2026-08-24-5.56
2026-08-23-6.83
2026-08-22-7.48
2026-08-21-4.29
2026-08-20-11.35
2026-08-19-14.69
2026-08-18-9.39
2026-08-17-10.38
2026-08-16-1.06
2026-08-15-2.13
2026-08-14-1.07
2026-08-13-10.75
2026-08-12-3.68
2026-08-11-3.13
2026-08-10+3.07
2026-08-09+1.44
2026-08-08-4.73
2026-08-07-1.71
2026-08-06-9.91

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 5-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 3 days-10 to -8 °F: 2 days-8 to -6 °F: 4 days-6 to -4 °F: 5 days-4 to -2 °F: 7 days-2 to 0 °F: 6 days0 to 2 °F: 1 day2 to 4 °F: 2 days4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.99 · P90 |e| 10.38 °F-200+20 °Fn = 31 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-20.00-18.000
-18.00-16.000
-16.00-14.001
-14.00-12.000
-12.00-10.003
-10.00-8.002
-8.00-6.004
-6.00-4.005
-4.00-2.007
-2.00+0.006
+0.00+2.001
+2.00+4.002
+4.00+6.000
+6.00+8.000
+8.00+10.000
+10.00+12.000
+12.00+14.000
+14.00+16.000
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08255.61 -5.25
2026-0162.26 -1.36

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-06 → 2026-08-30 31
GraphCast (IFS init)2026-01-06 → 2026-08-30 31
GraphCast (IFS init)2026-01-06 → 2026-08-30 30
GraphCast (IFS init)2026-01-06 → 2026-08-30 30

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (IFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 25 +0.05 [-0.64, 0.67] no
NCEP GFS 25 +1.43 [-2.02, 4.94] no
ECMWF IFS HRES 18 +1.77 [0.57, 4.11] yes
Persistence (baseline) 25 -0.31 [-6.67, 3.17] no

Cite this page

ShortCastCheck, KSEA graphcast_ifs lead 5, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/5/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model graphcast_ifs, lead day 5. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/5/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence